U.S. patent number 4,942,465 [Application Number 07/358,951] was granted by the patent office on 1990-07-17 for method of coding a digital video signal for reverse reproduction of pictures.
This patent grant is currently assigned to NEC Corporation. Invention is credited to Mutsumi Ohta.
United States Patent |
4,942,465 |
Ohta |
July 17, 1990 |
Method of coding a digital video signal for reverse reproduction of
pictures
Abstract
On subjecting a digital video signal of successive pictures to
redundancy reduction coding, a mode signal is produced which
indicates, as the redundancy reduction coding, a selected one of
interframe coding and intraframe coding. The digital video signal
is selectively subjected to the selected one of the interframe and
the intraframe coding in response to the mode signal. A particular
picture element of a current picture is subjected to the intraframe
coding when the mode signal indicates that the particular picture
element should be subjected to the interframe coding and that a
corresponding picture element of a following picture following the
current picture should be subjected to the intraframe coding. The
mode signal and results of the interframe and the intraframe coding
are multiplexed into a multiplexed signal. When a
motion-compensated coding is used instead of the interframe coding,
a specific picture element of the current picture is subjected to
the intraframe coding when the mode signal indicates that the
specific picture element should be subjected to the
motion-compensated coding and furthermore when the specific picture
element has no relation to a movement represented by each of motion
vectors which are used in carrying out the interframe coding on the
picture elements of the following picture.
Inventors: |
Ohta; Mutsumi (Tokyo,
JP) |
Assignee: |
NEC Corporation
(JP)
|
Family
ID: |
15105695 |
Appl.
No.: |
07/358,951 |
Filed: |
May 30, 1989 |
Foreign Application Priority Data
|
|
|
|
|
May 30, 1988 [JP] |
|
|
63-133477 |
|
Current U.S.
Class: |
375/240.13;
375/E7.256; 386/E5.014 |
Current CPC
Class: |
H04N
5/9262 (20130101); H04N 19/51 (20141101); H04N
5/85 (20130101) |
Current International
Class: |
H04N
5/926 (20060101); H04N 7/36 (20060101); H04N
5/84 (20060101); H04N 5/85 (20060101); H04N
007/137 () |
Field of
Search: |
;358/133,135,136 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Britton; Howard W.
Attorney, Agent or Firm: Ostrolenk, Faber, Gerb &
Soffen
Claims
What is claimed is:
1. A method of coding a digital video signal by subjecting said
digital video signal to redundancy reduction coding, said digital
video signal being representative of successive pictures, each
comprising a predetermined number of picture elements, said method
comprising the steps of:
producing a coding mode signal which indicates, as said redundancy
reduction coding, a selected one of interframe coding and
intraframe coding which are carried out with reference to a first
correlation factor between adjacent ones of said successive
pictures and a second correlation factor between the picture
elements within each of said successive pictures, respectively;
selectively coding said digital video signal into a first coded
signal by carrying out said selected one of the interframe and the
intraframe coding in response to said coding mode signal, said
first coded signal carrying a first result of said interframe
coding and a second result of said intraframe coding;
making said selectively coding step carry out said intraframe
coding on a particular element of the picture elements of a current
picture to produce a second coded signal when said coding mode
signal indicates that said particular element should be subjected
to said interframe coding and that a corresponding element of a
following picture should be subjected to said intraframe coding,
said following picture following said current picture in said
successive pictures, said corresponding element corresponding to
said particular element; and
multiplexing said first and said second coded signals and said
coding mode signal into a multiplexed signal.
2. A method of coding a digital video signal by subjecting said
digital video signal to redundancy reduction coding, said digital
video signal being representative of successive pictures, each
comprising a predetermined number of picture elements, said method
comprising the steps of:
producing a coding mode signal which indicates, as said redundancy
reduction coding, a selected one of interframe coding and
intraframe coding, said interframe coding being carried out by
detecting a motion vector representative of a movement of each
picture element between adjacent ones of said successive pictures
and by using said motion vector, said intraframe coding being
carried out by using a correlation between the picture elements
within each of said successive pictures;
selectively coding said digital video signal into a first coded
signal by carrying out said selected one of the interframe and the
intraframe coding in response to said coding mode signal, said
first coded signal carrying a first result of said interframe
coding and a second result of said intraframe coding;
making said selectively coding step carry out said intraframe
coding on a specific element of the picture elements of a current
picture to produce a second coded signal when said coding mode
signal indicates that said specific element should be subjected to
said interframe coding and furthermore when said specific element
has no relation to the movement represented by each of the motion
vectors which are used in carrying out said interframe coding on
the picture elements of a following frame when said coding mode
signal indicates that the picture elements of said following frame
should be subjected to said interframe coding, said following
picture following said current picture in said successive pictures;
and
multiplexing said first and said second coded signals, said motion
vectors, and said coding mode signal into a multiplexed signal.
3. A coding device for coding a digital video signal by subjecting
said digital video signal to redundancy reduction coding, said
digital video signal being representative of successive pictures,
each comprising a predetermined number of successive picture
elements, said coding device comprising:
producing means for producing a coding mode signal which indicates,
as said redundancy reduction coding, a selected one of interframe
coding and intraframe coding which are carried out with reference
to a first correlation factor between adjacent ones of said
successive pictures and a second correlation factor between the
picture elements within each of said successive pictures,
respectively;
selective coding means for selectively coding said digital video
signal into a first coded signal by carrying out said selected one
of the interframe and the intraframe coding in response to said
coding mode signal, said first coded signal carrying a first result
of said interframe coding and a second result of said intraframe
coding;
controlling means for controlling said selective coding means to
make said selective coding means carry out said intraframe coding
on a particular element of the picture elements of a current
picture to produce a second coded signal when said coding mode
signal indicates that said particular element should be subjected
to said interframe coding and that a corresponding element of a
following picture should be subjected to said intraframe coding,
said following picture following said current picture in said
successive pictures, said corresponding element corresponding to
said particular element; and
multiplexing means for multiplexing said first and said second
coded signals and said coding mode signal into a multiplexed
signal.
4. A coding device for coding a digital video signal by subjecting
said digital video signal to redundancy reduction coding, said
digital video signal being representative of successive pictures,
each comprising a predetermined number of picture elements, said
coding device comprising:
producing means for producing a coding mode signal which indicates,
as said redundancy reduction coding, a selected one of interframe
coding and intraframe coding, said interframe coding being carried
out by detecting a motion vector representative of a movement of
each picture element between adjacent ones of said successive
pictures and by using said motion vector, said intraframe coding
being carried out by using a correlation between the picture
elements within each of said successive pictures;
selective coding means for selectively coding said digital video
signal into a first coded signal by carrying out said selected one
of the interframe and the intraframe coding in response to said
coding mode signal, said first coded signal carrying a first result
of said interframe coding and a second result of said intraframe
coding;
controlling means for controlling said selective coding means to
make said selective coding means carry out said intraframe coding
on a specific element of the picture elements of a current picture
to produce a second coded signal when said coding mode signal
indicates that said specific element should be subjected to said
interframe coding and furthermore when said specific element has no
relation to the movement represented by each of the motion vectors
which are used in carrying out said interframe coding on the
picture elements of a following frame when said coding mode signal
indicates that the picture elements of said following frame should
be subjected to said interframe coding, said following picture
following said current picture in said successive pictures; and
multiplexing means for multiplexing said first and said second
coded signals, said motion vectors, and said coding mode signal
into a multiplexed signal.
Description
BACKGROUND OF THE INVENTION
This invention relates to a coding method of coding a digital video
signal by subjecting the digital video signal to redundancy
reduction coding. This invention relates also to a coding device
for use in carrying out the method.
Each of the successive pictures is called a frame when the digital
video signal is, for example, a television signal. Redundancy
reduction coding is effective to code the digital video signal into
a coded video signal having a low bit rate. As the redundancy
reduction coding, basic interframe predictive coding is known in
the art. The basic interframe predictive coding makes use of a
correlation factor between adjacent ones of the pictures or frames.
In the basic interframe predictive coding, the redundancy reduction
coding is carried out on a difference between corresponding picture
elements of two successive pictures to provide a result of the
basic interframe predictive coding.
Motion-compensated interframe predictive coding is also known in
the art as the redundancy reduction coding. In the
motion-compensated interframe predictive coding, a motion vector is
detected which represents a movement of each picture element
between two of pictures. The motion-compensated interframe
predictive coding carries out interframe predictive coding of the
digital video signal by using the motion vector.
Inasmuch as the motion-compensated interframe predictive coding is
also carried out by using a correlation factor between two adjacent
pictures like the basic interframe predictive coding, not only the
basic interframe predictive coding but also the motion-compensated
interframe predictive coding will be referred to as interframe
coding.
Intraframe or inframe coding is still also known in the art as the
redundancy reduction coding. The intraframe coding is carried out
by using a correlation factor between the picture elements within
each of the pictures. The intraframe coding is, for example, PCM
(pulse code modulation) coding, intraframe predictive coding,
orthogonal transformation coding, or vector quantization
coding.
Such redundancy reduction coding is generally used in transmitting
the digital video signal. However, the redundancy reduction coding
is also used in a video signal processing system which is for use
in a recording medium, such as a compact disk read-only memory
(CD-ROM), to record and/or reproduce the digital video signal.
In the meanwhile, it may be preferable that the compact disk
read-only memory can be operable like a video tape in performing
not only a normal reproduction but also various other functions,
such as a reverse reproduction, a high speed reproduction, scene
skipping, an arbitrary reproduction of an arbitrary scene. However,
it is difficult to perform the reverse reproduction when the
digital video signal is subjected to the interframe coding alone.
More specifically, the digital video signal is divided into a
zeroth or leading frame to an end or trailing frame as leading
through trailing compressed video signals subjected to the
interframe coding. The digital video signal is successively
recorded on the recording medium from the leading compressed video
signal to the trailing compressed video signal in a normal order.
Merely for convenience of description, the zeroth through the end
frames may be understood to correspond to zeroth through end
scenes, respectively. On carrying out the reverse reproduction, the
digital video signal is reproduced from the recording medium in a
reverse order from the end scene in response to a request issued by
an operator or user to indicate the reverse reproduction.
In order to perform the reverse reproduction, an improved method is
disclosed in a prior U.S. patent application Ser. No. 189,249 which
was filed May 2, 1988, by Toshio Koga, Junichi Ohki, Mutsumi Ohta,
and Hideto Kunihiro for assignment to the present assignee and c/o
NEC Home Electronics, Ltd. The above-named Mutsumi Ohta is the
instant applicant. The Ohta et al patent application corresponds to
a prior Canadian patent application No. 565,485 which was filed
Apr. 29, 1988. In the prior patent applications, the video signal
processing system is called an image processing system. The digital
video signal is called a sequence of image signals. In the improved
method, the digital video signal is coded with the leading and the
trailing frames subjected to the intraframe predictive coding and
with the remaining frames subjected to the interframe predictive
coding. According to the improved method, it is possible to carry
out not only the normal reproduction but also the reverse
reproduction. The improved method is, however, defective in that
the reverse reproduction can not be performed when an
interframe/intraframe adaptive coding is used as the redundancy
reduction coding. In the interframe/intraframe adaptive predictive
coding, the digital video signal is decoded into a decoded signal
with a first result of the interframe coding and a second result of
the intraframe coding alternatingly appearing in the coded signal.
More specifically, the interframe coding and the intraframe coding
are adaptively alternatingly carried out in consideration of an
amount of produced information of the first result and another
amount of produced information of the second result.
SUMMARY OF THE INVENTION
It is therefore a general object of this invention to provide a
method of coding a digital video signal, whereby reverse
reproduction can be performed when interframe/intraframe adaptive
coding is used in coding the digital video signal.
Other objects of this invention will become clear as the
description proceeds.
A method to which this invention is applicable is for coding a
digital video signal by subjecting the digital video signal to
redundancy reduction coding. The digital video signal is
representative of successive pictures, each comprising a
predetermined number of picture elements. According to an aspect of
this invention, the method comprises the steps of (a) producing a
coding mode signal which indicates, as the redundancy reduction
coding, a selected one of interframe coding and intraframe coding
which are carried out with reference to a first correlation factor
between adjacent ones of the successive pictures and a second
correlation factor between the picture elements within each of the
successive pictures, respectively, (b) selectively coding said
digital video signal into a first coded signal by carrying out the
selected one of the interframe and the intraframe coding in
response to the coding mode signal, the first coded signal carrying
a first result of the interframe coding and a second result of the
intraframe coding, (c) making the selectively coding step carry out
the intraframe coding on a particular element of the picture
elements of a current picture to produce a second coded signal when
the coding mode signal indicates that the particular element should
be subjected to the interframe coding and that a corresponding
element of a following picture should be subjected to the
intraframe coding, the following picture following the current
picture in the successive pictures, the corresponding element
corresponds to the particular element, and (d) multiplexing the
first, and the second coded signals and the coding mode signal into
a multiplexed signal.
According to another aspect of this invention, the method
comprising the steps of (a) producing a coding mode signal which
indicates, as the redundancy reduction coding, a selected one of
interframe coding and intraframe coding, the interframe coding
being carried out by detecting a motion vector representative of a
movement of each picture element between adjacent ones of the
successive pictures and by using said motion vector, the intraframe
coding being carried out by using a correlation between the picture
elements within each of the successive pictures, (b) selectively
coding the digital video signal into a first coded signal by
carrying out the selected one of the interframe and the intraframe
coding in response to the coding mode signal, the first coded
signal carrying a first result of the interframe coding and a
second result of the intraframe coding, (c) making the selectively
coding step carry out the intraframe coding on a specific element
of the picture elements of a current picture to produce a second
coded signal when the coding mode signal indicates that the
specific element should be subjected to the interframe coding and
furthermore when the specific element has no relation to the
movement represented by each of the motion vectors which are used
in carrying out the interframe coding on the picture elements of a
following frame when the coding mode signal indicates that the
picture elements of the following frame should be subjected to the
interframe coding, the following picture following the current
picture in the successive pictures, and (d) multiplexing the first
and the second coded signals, the motion vectors, and the coding
mode signal into a multiplexed signal.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a diagram for use in describing a coding method according
to a first embodiment of this invention;
FIG. 2 is another diagram for use in describing the coding method
according to the first embodiment of this invention;
FIG. 3 is still another diagram for use in describing the coding
method according to the first embodiment of this invention;
FIG. 4 is yet another diagram for use in describing the coding
method according to the first embodiment of this invention;
FIG. 5 is a diagram for use in describing a coding method according
to a second embodiment of this invention;
FIG. 6 is another diagram for use in describing the coding method
according to the second embodiment of this invention;
FIG. 7 is still another diagram for use in describing the coding
method according to the second embodiment of this invention;
FIG. 8 is a block diagram of a coding device for use in carrying
out the coding method according to the first embodiment of this
invention;
FIG. 9 is a block diagram of a processing circuit for use in the
coding device illustrated in FIG. 8;
FIG. 10 is a block diagram of a coding device for use in carrying
out the coding method according to the second embodiment of this
invention;
FIG. 11 is a block diagram of a processing circuit for use in the
coding device illustrated in FIG. 10;
FIG. 12 is a block diagram of another coding device for use in
carrying out the coding method according to the second embodiment
of this invention;
FIG. 13 shows, in blocks and together with a recording medium, a
decoding device for decoding a read-out signal read out of the
recording medium on which an output signal of the coding device
illustrated in FIG. 8 is recorded;
FIG. 14 shows, in blocks and together with a recording medium, a
decoding device for decoding a read-out signal read out of the
recording medium on which an output signal of the coding device
illustrated in FIG. 10 is recorded;
FIG. 15 shows, in blocks and together with a recording medium,
another decoding device for decoding a read-out signal read out of
the recording medium on which an output signal of the coding device
illustrated in FIG. 8 is recorded;
FIG. 16 is a block diagram of a vector & mode processing
circuit for use in each of the decoding device illustrated in FIGS.
14 and 15; and
FIG. 17 is a block diagram of another vector & mode processing
circuit for use in each of the decoding devices illustrated in
FIGS. 14 and 15.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIG. 1, description will now be made as regards a
coding method according to a first embodiment of this invention.
Attention will be directed at first to a basic interframe
predictive coding method. It will be assumed that a (j, k)-th
picture element of an i-th frame of a digital video signal is
represented by X(i, j, k), where i is equal to one of integers 0, .
. . , and n. Likewise, j is equal to one of integers 1, . . . , and
p while k is equal to one of integers 1, . . . , and q. Further
supposing that an interframe predictive error signal (namely, an
interframe difference signal) is represented by E(i, j, k), the
interframe predictive error signal E(i, j, k) is represented by
Formula (1) hereunder:
In the basic interframe predictive coding method, the interframe
predictive error signal E(i, j, K) is calculated at first. The
interframe predictive error signal E(i, j, k) is subsequently coded
into a coded predictive error signal. In order to carry out a
normal reproduction of the picture element X(i, j, k) by decoding
the coded predictive error signal in a decoder, the picture element
X(i, j, k) is obtained by Formula (2) hereunder which is given by
modification of Formula (1):
It should be noted here that picture elements x(0, j, k) of the
zeroth frame or picture are given to the decoder in order to carry
out the normal reproduction by using Formula (2). In general, first
and second method are used in order to supply the decoder with the
picture elements X(0, j, k) of the zeroth picture. In the first
method, the picture elements X(0, j, k) of the zeroth picture are
coded by intraframe coding described in the preamble of the instant
specification. In the prior patent application described in the
preamble of the instant specification, the picture elements X(0, j,
k) of the zeroth picture are coded by using an intraframe
predictive coding as the intraframe coding. In the second method,
the zeroth picture is preliminarily determined to have a fixed
picture.
Description will proceed to a reverse reproduction. In order to
carry out the reverse reproduction of the picture elements X(i, j,
k), the picture elements X(i, j, k) are successively decoded by the
decoder from the n-th frame to the zeroth frame by Formula (3)
hereunder which is given by different modification of Formula
(1):
In this case, picture elements X(n, j, k) of the n-th or trailing
picture should be obtained by the decoder. In order to carry out
the reverse reproduction, the picture elements X(n, j, k) of the
n-th picture are also coded by the intraframe coding. In the prior
patent application described in the preamble of the instant
specification, the picture elements X(n, j, k) of the n-th picture
are coded by using the intraframe predictive coding as the
intraframe coding.
Thus, the digital video signal is coded in the prior patent
application with the zeroth and the n-th pictures subjected to
intraframe predictive coding and with the remaining pictures
subjected to intraframe predictive coding. However, the reverse
reproduction can not be performed according to the prior patent
application when interframe/intraframe adaptive coding is used as
redundancy reduction coding. This incapability of the reverse
reproduction will be described hereunder.
In FIG. 1, it will be assumed that each frame of the digital video
signal is represented by a one-dimensional signal merely for
convenience of the description although each frame cf the digital
video signal is a two-dimensional signal in fact. In FIG. 1, an
interframe predictive error signal of a j-th picture element of an
i-th frame is represented by E(i, j). The interframe predictive
error signal E(i, j) is equivalent to a first result of interframe
predictive coding when the j-th picture element of the i-th frame
is subjected to the interframe predictive coding. An intraframe
coded signal of the j-th picture element of the i-th frame is
represented by P(i, j). The intraframe coded signal P(i, j) is
equivalent to a second result of intraframe coding when the j-th
picture element of the i-th frame is subjected to the intraframe
coding.
In order to perform the normal reproduction, all of the picture
elements of the zeroth frame are subjected to the intraframe
predictive coding to produce second results P(0, 1), P(0, 2), P(0,
3), and P(0, 4). All of the picture elements of the first frame are
subjected to the basic interframe predictive coding to produce
first results E(1, 1), E(1, 2), E(1, 3), and E(1, 4).
A first picture element of the second frame is subjected to the
basic intraframe predictive coding to produce a second result P(2,
1). Second through fourth picture elements of the second frame are
subjected to the basic interframe predictive coding to produce
first results E(2, 2), E(2, 3), and E(2, 4).
For the third frame, first, second, and fourth picture elements are
subjected to the basic interframe predictive coding to produce
first results E(3, 1), E(3, 2), and E(3, 4). A third picture
element of the third frame is subjected to the intraframe
predictive coding to produce a second result P(3, 3). For the
fourth frame, first through fourth picture elements are subjected
to the basic interframe predictive coding to produce first results
E(4, 1), E(4, 2), E(4, 3), and E(4, 4).
It will be assumed merely for brevity of the description that the
fourth frame is the trailing frame. In order to perform the reverse
reproduction, all of the Picture elements of the fourth frame are
subjected to the intraframe coding to produce second results P(4,
1), P(4, 2), P(4, 3), and P(4, 4).
Turning to FIG. 2, the first and the second results E and P are
represented for use in carrying out the normal reproduction.
Turning back to FIG. 1, it is impossible to decode the first
picture element of the first frame and the third picture element of
the second frame when the reverse reproduction is carried out in
accordance with Formula (3). This is because the first results E(2,
1) and E(3, 3) are not produced.
In order to resolve this problem, the first picture element of the
first frame and the third picture element of the second frame are
subjected to the intraframe coding to produce second results P(1,
1) and P(2, 3) in accordance with this invention. In FIG. 1, a
symbol * is attached to the right upper portion of each of the
second results P(1, 1), P(2, 3), P(4, 1), P(4, 2), P(4, 3), and
P(4, 4) which are used in carrying out the reverse reproduction and
are not used in carrying out the normal reproduction.
Turning to FIG. 3, the first and the second results E and P are
represented for use in carrying out the reverse reproduction.
Turning to FIG. 4, the first and the second results E and P are
represented for use in carrying out not only the normal
reproduction but also the reverse reproduction.
Turning back to FIG. 1 again, a method according to the first
embodiment of this invention will be described more in detail. The
method is for coding a digital video signal by subjecting the
digital video signal to redundancy reduction coding. The digital
video signal is representative of successive pictures, each of
which comprises a predetermined number of picture elements.
It will be assumed for a short while that the interframe/intraframe
adaptive coding is used in coding the digital video signal.
According to the embodiment being described, the method comprises a
producing step wherein a coding mode signal is produced which
indicates, as the redundancy reduction coding, a selected one of
the basic interframe predictive coding and the intraframe
coding.
In a selectively coding step, the digital video signal is
selectively coded into a first coded signal by carrying out the
selected one of the basic interframe predictive coding and the
intraframe coding in response to the coding mode signal. The first
coded signal carries a first result E of the basic interframe
predictive coding and a second result P of the intraframe
coding.
The selectively coding step is made to carry out the intraframe
predictive coding on a particular element (for example, the first
picture element of the first frame) of the picture elements of a
current picture (that is, the first frame) to produce a second
coded signal P(1, 1) when the coding mode signal indicates that the
particular element should be subjected to the basic interframe
predictive coding and that a corresponding element (that is, the
first picture element of the second frame) of a following picture
(that is, the second frame) should be subjected to the intraframe
coding. The following picture follows the current picture in the
successive pictures. The corresponding element corresponds to the
particular element.
In due course, a second frame or picture becomes the current
picture. At this stage of coding, the particular element
corresponds to the third picture element of the second frame while
the corresponding picture of the following picture corresponds to
the third picture element of the third frame. In this event, the
selectively coding step produces the second coded signal P(2,
3).
The first and the second coded signals and the coding mode signal
are multiplexed into a multiplexed signal.
Description will be made as regards a feature of the method. It
will be assumed that S(i, j) represents the coding mode signal of
the j-th picture element of the i-th frame. When the coding mode
signal S(i, j) represents the intraframe coding, the first result
E(i, j) of the basic interframe predictive coding is not produced.
Inasmuch as the first result E(i, j) is not produced, it is
impossible to carry out the reverse reproduction of the j-th
picture element of the (i-1)-th frame. In order to realize the
reverse reproduction of the j-th picture element of the (i-1)-th
frame, the intraframe coding is carried out on the j-th picture
element of the (i-1)-th frame to produce the second result P(i-1,
j). That is, not only the basic interframe predictive coding but
also the intraframe coding are carried out on the j-th picture
element of the (i-1)-th frame.
Referring to FIG. 5, description will proceed to a coding method
according to a second embodiment of this invention. Attention will
be directed to a motion compensated interframe predictive coding
method. It will be assumed that a motion vector of the picture
element X(i, j, k) is represented by V(i, j, k) and that the motion
vector V(i, j, k) is represented by:
V(i, j, k) =(vx(i, j, k), vy(i, j, k)), where vx(i, j, k) and vy(i,
j, k) represent horizontal and vertical components of the motion
vector V(i, j, k), respectively. An interframe predictive error
signal E(i, j, k) is represented by Formula (4) hereunder:
In the motion-compensated interframe predictive coding method, the
interframe predictive error signal E(i, j, k) and the motion vector
V(i, j, k) are coded into a coded predictive error signal and a
coded vector, respectively. In order to carry out a normal
reproduction of the picture element X(i, j, k) by decoding the
coded predictive error signal and the coded vector in a decoder,
the picture element X(i, j, k) is obtained by Formula (5) hereunder
which is given by modification of Formula (4):
In order to realize the normal reproduction by using Formula (5),
the picture elements X(0, j, k) of the zeroth frame are given to
the decoder. For this purpose, the picture elements X(0, j, k) of
the zeroth picture are coded by using the intraframe coding.
Description will proceed to a reverse reproduction. In order to
carry out the reverse reproduction of the picture elements X(i, j,
k), the picture elements X(i, j, k) are successively decoded from
the n-th frame to the zeroth frame by Formula (6) hereunder which
is given by different modification of Formula (4):
In order to carry out the reverse reproduction by using Formula
(6), the picture elements X(n, j, k) of the n-th or trailing frame
are given to the decoder. For this purpose, the picture elements
X(n, j, k) of the n-th picture are coded by using intraframe
coding.
However, the reverse reproduction can not be performed only by
decoding the picture elements X(n, j, k) of the n-th picture by
using the intraframe predictive coding. This incapability of the
reverse reproduction will be described hereunder.
In FIG. 5, each frame of the digital video signal is represented by
a one-dimensional signal like in FIG. 1. In FIG. 5, a motion vector
of a j-th picture element of an i-th frame is represented by V(i,
j) while an interframe predictive error signal (namely, the first
result of the motion-compensated interframe predictive coding) of
the j-th picture element of the i-th frame is represented by E(i,
j). An intraframe coded signal (namely, the second result of the
intraframe predictive coding) of the j-th picture element of the
i-th frame is represented by P(i, j).
In order to perform the normal reproduction, all of the picture
elements of the zeroth frame are subjected to the intraframe coding
to produce the second results P(0, 1), P(0, 2), P(0, 3), and P(0,
4). All of the picture elements of the first frame are subjected to
the motion-compensated interframe predictive coding to produce the
first results E(1, 1), E(1, 2), E(1, 3), and E(1, 4) and the motion
vectors V(1, 1), V(1, 2), V(1, 3) and V(1, 4).
First through third picture elements of the second frame are
subjected to the motion-compensated interframe predictive coding to
produce the first results E(2, 1), E(2, 2), and E(2, 3) and the
motion vectors V(2, 1), V(2, 2), and V(2, 3). A fourth picture
element of the second frame is subjected to the intraframe coding
to produce the second result P(2, 4).
For the third and the fourth frames, all of the picture elements
are subjected to the motion-compensated interframe predictive
coding to produce the first result E(3, 1), E(3, 2), E(3, 3), E(3,
4), E(4, 1), E(4, 2), E(4, 3), and E(4, 4) and the motion vectors
V(3, 1), V(3, 2), V(3, 3), V(3, 4), V(4, 1), V(4, 2), V(4, 3), and
V(4, 4).
In order to perform the reverse reproduction, all of the picture
elements of the trailing frame, namely, the fourth frame, are
subjected to the intraframe coding to produce the second results
P(4, 1), P(4, 2), P(4, 3), and P(4, 4).
Description will be made more in detail as regards the
motion-compensated interframe coding of the first picture element
of the second frame. The motion-compensated interframe predictive
coding is carried out by detecting the motion vector V(2, 1) and by
using the motion vector V(2, 1). The motion vector V(2, 1)
represents a movement from the second picture element of the first
frame to the first picture element of the second frame in FIG. 5.
In other words, motion-compensated interframe coding of the first
picture element of the second frame is carried out with reference
to the second picture element of the first frame. The
motion-compensated interframe coding of each of the second and the
third picture elements of the third frame is carried out with
reference to the third picture element of the second frame.
Likewise, the motion-compensated interframe predictive coding of
the first picture element of the first frame is carried out with
reference to the first picture element of the zeroth frame.
Turning to FIG. 6, the first and the second results E and P and the
motion vectors V are represented for use in carrying out the normal
reproduction.
Turning back to FIG. 5, when the reverse reproduction is carried
out in accordance with Formula (6), it is impossible to decode the
first picture element of the first frame and the first picture
element of the second frame for the reason which will be described
hereunder. Attention will be directed to the first picture element
of the first frame. The first picture element of the first frame
has no relation to the movement represented by each of the motion
vectors V(2, 1), V(2, 2), V(2, 3), and V(2, 4) which are used in
carrying out the motion-compensated predictive coding on the
picture elements cf the second frame which follows the first frame.
That is, the motion-compensated interframe predictive coding of the
picture elements of the second frame is carried out without
reference to the first picture element of the first frame.
Likewise, the first picture element of the second frame has no
relation to the movement represented by each of the motion vectors
V(3, 1), V(3, 2), V(3, 3), and V(3, 4) which are used in carrying
out the motion-compensated predictive coding on the picture
elements of the third frame.
This is the reason why the first picture element of the first frame
and the first picture element of the second frame can not be
decoded when the reverse reproduction is carried out.
In order to resolve this problem, the first picture element of the
first frame and the first picture element of the second frame are
subjected to the intraframe coding to produce the second results
P(1, 1) and P(2, 1) in accordance with this invention. In FIG. 5, a
symbol * is again attached to the right upper portion of each of
the second results P(1, 1), P(2, 1), P(4, 1), P(4, 2), P(4, 3), and
P(4, 4) which are used in carrying out the reverse reproduction and
which are not used in carrying out the normal reproduction.
Turning to FIG. 7, the first and the second results E and P and the
motion vectors V are represented for use in carrying out the
reverse reproduction.
Turning back to FIG. 5 again, a method according to the second
embodiment of this invention will be described in detail. The
method comprises a producing step wherein production is made about
a coding mode signal which indicates a selected one of the
motion-compensated interframe predictive coding and the intraframe
coding when the motion-compensated interframe/intraframe adaptive
coding is used in the digital video signal. The motion-compensated
interframe predictive coding is carried out by detecting a motion
vector representative of a movement of each picture element between
adjacent ones of successive pictures of the digital video signal.
The intraframe coding is carried out by using a correlation between
the picture elements within each of the successive pictures.
In a selectively coding step, the digital video signal is
selectively coded into a first coded signal by carrying out the
selected one of the motion-compensated interframe predictive coding
and the intraframe coding in response to the coding mode signal.
The first coded signal carries a first result E of the motion
compensated interframe predictive coding and a second result P of
the intraframe coding.
The selectively coding step is made to carry out the intraframe
coding on a specific element (for example, the first picture
element of the first frame) of the picture elements of a current
picture (that is, the first frame) to produce a second coded signal
P(1, 1) when the coding mode signal indicates that the specific
element should be subjected to the motion-compensated interframe
predictive coding and furthermore when the specific element has no
relation to the movement represented by each of the motion vectors
V(2, 1), V(2, 2), and V(2, 3). The motion vectors V(2, 1), V(2, 2),
and V(2, 3) are used in carrying out the motion-compensated
interframe predictive coding on the picture elements of a following
frame (that is, the second frame) when the coding mode signal
indicates that the picture elements of the following frame should
be subjected to the motion-compensated interframe predictive
coding. The following picture follows the current picture in the
successive pictures.
When the second frame becomes the current picture, the specific
element corresponds to the first picture element of the second
frame. In this event, the selectively coding step produces the
second result P(2, 1).
The first and the second coded signals, the motion vectors, and the
coding mode signal are multiplexed into a multiplexed signal.
Description will be made as regards a method for detecting the
specific element by the use of Formula (6). Supposing in Formula
(6) that:
Formula (6) is modified into Formula (8) hereunder:
When first and second integers are given as a and b, respectively,
judgment is made whether or not third and fourth integers are
obtained as j and k, respectively, by using Formula (7). When a
result of the judgement indicates that it is impossible to obtain
the third and the fourth integers, it will be understood that the
motion-compensated interframe predictive coding is carried out on
the picture elements of the i-th frame with no reference to a
picture element X(i-1, a, b). That is, the picture element X(i-1,
a, b) is the specific element. Therefore, the intraframe coding is
carried out on the picture element X(i-1, a, b).
Referring to FIG. 8, description will proceed to a coding device
for use in carrying out the method according to the first
embodiment of this invention. That is, the coding device is capable
of carrying out the interframe/intraframe adaptive coding described
above.
The coding device is for coding the digital video signal by
subjecting the digital video signal to redundancy reduction coding.
The decoding device comprises a basic interframe predictive coder
41 and an intraframe coder 42. Responsive to the digital video
signal, the basic interframe predictive coder 41 carries out, as
the redundancy reduction coding, the basic interframe predictive
coding to produce an interframe predictive error signal E as a
first result of the basic interframe predictive coding. Responsive
to the digital video signal, the intraframe coder 42 carries out,
as the redundancy reduction coding, the intraframe coding of, for
example, intraframe predictive coding to produce an intraframe
coded signal P as a second result of the intraframe coding.
Responsive to the first and the second result E and P, a mode
signal producing circuit 43 produces a coding mode signal S which
represents for each picture element a selected one of the basic
interframe predictive coding and the intraframe coding in
consideration of a first amount of produced information of the
first result E and a second amount of produced information of the
second result P. More specifically, the mode signal producing
circuit 43 compares the first and the second amounts and produces a
compared result signal. When the compared result signal represents
that the first amount is smaller than the second amount, the mode
signal producing circuit 43 produces the coding mode signal S which
has a logic "0" level to represent the basic interframe predictive
coding. When the compared result signal represents that the first
amount is not smaller than the second amount, the mode signal
producing circuit 43 produces the coding mode signal S which has a
logic "1" level to represent the intraframe coding. Inasmuch as the
mode signal producing circuit 43 is known in the art, details will
no more be described.
When the coding mode signal S is used for the coders 41 and 42 in
coding of a succeeding part of the digital video signal, the coding
signal is supplied to the coders 41 and 42.
Responsive to the first result E, a first delay circuit 45 delays
the first result E to produce a first delayed signal by providing a
delay which is equal to a period of each frame or picture.
Likewise, a second delay circuits 46 delays the second result P to
produce a second delayed signal by providing the delay equal to the
period of each frame. A third delay circuit 47 delays the coding
mode signal S to produce a delayed mode signal by providing the
delay equal to the period of each frame.
Responsive to the coding mode signal S, a processing circuit 48
processes the coding mode signal S into a processed mode signal S'
which has a logic "1" level to represent the intraframe coding for
picture elements which are necessary on carrying out the reverse
reproduction and the normal reproduction. The above-mentioned
particular elements are included in the picture elements.
Responsive to the first delayed signal and the delayed mode signal,
a first selector 49 selects the first delayed signal as a first
selected signal only when the delayed mode signal has a logic "0"
level to represent the basic interframe predictive coding.
Responsive to the second delayed signal and the processed mode
signal, a second selector 50 selects the second delayed signal as a
second selected signal only when the processed mode signal S' has a
logic "1" level to represent the intraframe coding.
A multiplexer 51 multiplexes the first and the second selected
signals and the delayed mode signal into the multiplexed
signal.
Referring to FIG. 9, the processing circuit 48 comprises a fourth
delay circuit 52 and an OR gate 53. The fourth delay circuit 52
delays the coding mode signal S to produce another delayed mode
signal by providing the delay equal to a period of each frame or
picture. The other delayed mode signal is equivalent to the delayed
mode signal produced by the third delay circuit 47 illustrated in
FIG. 8. Responsive to the coding mode signal S and the other
delayed signal, the OR gate 53 produces an OR'ed signal as the
processed mode signal S'.
Reviewing FIGS. 8 and 9, the mode signal producing circuit 43
serves as a producing arrangement for producing the coding mode
signal S which indicates a selected one of the basic interframe
predictive coding and the intraframe coding. A combination of the
interframe and the intraframe coders 41 and 42, the first through
the third frame delay circuits 45 to 46, and the first and the
second selectors 49 and 50 is operable as a selective coding
arrangement. The selective coding arrangement selectively codes the
digital video signal into a first coded signal by carrying out the
selected one of the basic interframe predictive coding and the
intraframe coding in response to the coding mode signal S. The
first coded signal carries the first and the second results E and
P.
The processing circuit 48 serves as a controlling arrangement. The
controlling arrangement controls the selective coding arrangement
to make the selective coding arrangement carry out the intraframe
coding on a particular element of the picture elements of a current
picture to produce a second coded signal when the coding mode
signal S indicates that the particular element should be subjected
to the basic interframe predictive coding and that a corresponding
element of a following picture should be subjected to the
intraframe coding. The following picture follows the current
picture in the successive pictures. The corresponding element
corresponds to the particular element. The multiplexer 51 serves as
a multiplexing arrangement which multiplexes the first and the
second coded signals and the coding mode signal S into a
multiplexed signal.
Referring to FIG. 10, description will proceed to a coding device
for use in carrying out the method according to the second
embodiment of this invention. That is, the coding device is capable
of carrying out the motion-compensated interframe predictive coding
described above.
The coding device is similar to the coding device illustrated in
FIG. 8 except for the following. A motion-compensated predictive
coder 54 is used instead of the basic interframe predictive coder
41 illustrated in FIG. 8. The motion-compensated predictive coder
54 carries out the motion-compensated interframe predictive coding
to produce an interframe predictive error signal E as a first
result of the motion-compensated interframe predictive coding. In
this event, the motion-compensated predictive coder 54 also
produces a motion vector V described above. The mode signal
producing circuit 43 produces a coding mode signal S which
represents for each picture element a selected one of the
motion-compensated interframe predictive coding and the intraframe
predictive coding in consideration of a first amount of produced
information of the first result E and a second amount of produced
information of the second result P.
Each of the first, the second, and the third delay circuits 45, 46,
and 47 provides a delay which is equal to twice a period of each
frame or picture. A fifth delay circuit 55 delays the motion vector
V to produce a delayed vector V by providing a delay which is equal
to twice a period of each frame.
As will presently be described, the processing circuit 48 processes
the coding mode signal S into a processed mode signal S' with
reference to the motion vector V.
Responsive to the delayed vector and the delayed mode signal
produced by the third delay circuit 47, a third selector 56 selects
the delayed vector V as a selected vector only when the delayed
mode signal represents the motion-compensated interframe predictive
coding. Only when the delayed mode signal represents the
motion-compensated interframe predictive coding, the first selector
49 selects an output signal of the first delay circuit 45, namely,
the first delayed signal, as the first selected signal.
The multiplexer 51 multiplexes the delayed vector, the delayed mode
signal, and output signals of the first and the second selectors 49
and 50, namely, the first and the second selected signals, into the
multiplexed signal.
Turning to FIG. 11, the processing circuit 48 of the coding device
illustrated in FIG. 10 is similar to that illustrated in FIG. 9
except for the following. The fourth delay circuit 52 delays the
coding mode signal S to produce the delayed mode signal by
providing a delay equal to twice a period of each frame or picture.
The delayed mode signal is a normal mode signal which is used in
carrying out the normal reproduction. A combination of a memory 57
and subtractors 58 and 59 receives the coding mode signal S and the
horizontal and vertical components Vx and Vy of the motion vector V
to produce a reverse mode signal S" which is for use in carrying
out the reverse reproduction. More specifically, the reverse mode
signal S" has a logic "1" level so as to represent the intraframe
coding for picture elements which are necessary on carrying out the
reverse reproduction. The above-mentioned specific elements are
included in the picture elements. Supplied with the normal mode
signal and the reverse mode signal S", the OR gate 53 produces an
OR'ed signal as the processed mode signal S'.
Description is now made as regards the combination of the memory 57
and subtractors 58 and 59 in detail. It will be assumed that a
picture element address corresponding to a picture element location
of the motion vector V is represented by i, j. The subtractor 58
subtracts the horizontal component Vx from a horizontal component j
of the picture element address to produce a first subtraction
result a of the subtraction. The subtractor 59 subtracts the
vertical component Vy from a vertical component k of the picture
element address k to produce a second subtraction result b of the
subtraction.
Supplied with a memory address of the memory 57 that is indicated
by the first and the second subtraction results a and b, the memory
57 memorizes an input signal I in the memory address as a memorized
signal only when the coding mode signal S indicates the
motion-compensated interframe predictive coding. For this purpose,
the coding mode signal S is supplied to an enable terminal of the
memory 57. As a result, the input signal I is never memorized in
the memory 57 when the coding mode signal S indicates the
intraframe coding. The input signal I indicates the
motion-compensated interframe predictive coding mode and is of, for
example, a logic "0" level. After a lapse of a period of each frame
or picture, the memorized signal is read out of the memory 57 as
the reverse mode signal S" in response to an output address
supplied to the memory 57.
After the reverse mode signal S" is read out of the memory 57,
another input signal (not shown) representative of the intraframe
coding must be memorized in the memory 57 as another memorized
signal in order to produce a following reverse mode signal S". The
other input signal is, for example, a logic "1" level. For this
purpose, a content of the memory 57 is erased when the memory 57
receives a frame pulse which is generated in synchronism with a
leading part of each frame. The following reverse mode signal S"
has a logic "1" level to represent the intraframe coding even for
the above-mentioned specific elements which are detected in the
manner described in conjunction with Formulas (7) and (8).
Reviewing FIGS. 10 and 11, the mode signal producing circuit 43
serves as another producing arrangement for producing the coding
mode signal S which indicates a selected one of the
motion-compensated interframe predictive coding and the intraframe
coding. A combination of the motion-compensated predictive coder
54, the intraframe coder 42, the first through third delay circuits
45 to 47, the fifth delay circuit 55, and the first, the second,
and the third selectors 49, 50, and 56 is operable as another
selective coding arrangement. The selective coding arrangement
selectively codes the digital video signal into a first coded
signal by carrying out the selected one of the motion-compensated
interframe predictive coding and the intraframe coding in response
to the coding mode signal S. The first coded signal carries the
first and the second results E and P.
The processing circuit 48 serves as another controlling
arrangement. The controlling arrangement controls the other
selective coding arrangement carry out the motion-compensated
interframe predictive coding on a specific element of the picture
elements of a current picture to produce a second coded signal when
the coding mode signal S indicates that the specific element should
be subjected to the motion-compensated interframe predictive coding
and furthermore when the specific element has no relation to the
movement represented by each of the motion vectors V which are used
in carrying out the motion-compensated interframe predictive coding
on the picture elements of a following frame when the coding mode
signal indicates that the picture elements of the following frame
should be subjected to the motion-compensated interframe predictive
coding. The following picture follows the current picture in the
successive pictures.
The multiplexer 51 serves as another multiplexing arrangement which
multiplexes the first and the second coded signals, the motion
vectors V, and the coding mode signal S into a multiplexed
signal.
Referring tc FIG. 12, description will proceed to another coding
device for use in carrying out the method according to the second
embodiment of this invention. In the coding device, orthogonal
transformation coding is used as the intraframe coding.
The coding device is similar to that illustrated in FIG. 10 except
that an orthogonal transformation coder 61 and a minimum
transformation coefficient producing circuit 62 are used instead of
the intraframe coder 42 and the second selector 50, respectively,
and that the second delay circuit 46 is supplied with the digital
video signal.
Responsive to the digital video signal, the orthogonal
transformation coder 61 carries out orthogonal transformation
coding of the digital video signal to produce an orthogonal
transformation coded signal as a result of the orthogonal
transformation coding. The result of the orthogonal transformation
coding is supplied only to the mode signal producing circuit 43.
The second delay circuit 46 delays the digital video signal to
produce a delayed video signal by providing a delay which is equal
to twice a period of each frame.
Responsive to the processed mode signal S', the minimum
transformation coefficient producing circuit 62 selects the delayed
video signal as a selected video signal only when the processed
mode signal S' has a logic "1" level to represent the orthogonal
transformation coding. Thereafter, the minimum transformation
coefficient producing circuit 62 carries out orthogonal
transformation coding on the selected video signal to produce
another orthogonal transformation coded signal as the second result
P of the orthogonal transformation coding.
In this event, the minimum, transformation coefficient producing
circuit 62 carries out the orthogonal transformation coding by
using a minimum transformation coefficient which is determined on
the basis of linear programming so that an amount of produced
information of the second result P becomes minimum. The second
result P of the orthogonal transformation coding is directly
supplied to the multiplexer 51.
In the decoding device illustrated in FIG. 12, a combination of the
motion-compensated coder 54, the orthogonal transformation coder
61, the first through the third delay circuits 45 to 47, the fifth
delay circuit 55, the first and the third selectors 49 and 56, and
the minimum transformation coefficient producing circuit 62 is
operable as still another selective coding arrangement. The
selective coding arrangement selectively codes the digital video
signal into the first coded signal by carrying out the selected one
of the motion-compensated interframe predictive coding and the
intraframe coding (that is, the orthogonal transformation coding)
in response to the coding mode signal S. The first coded signal
carries the first and the second results E and P.
Referring to FIG. 13, a decoding device 65 is for use in
combination with a recording medium 66. The decoding device 65 is
for decoding a read-out signal read out of the recording medium 66
on which an output signal of the coding device illustrated in FIG.
8 is successively recorded. The output signal of the coding device
illustrated in FIG. 8 is equivalent with the multiplexed signal
produced by the coding device illustrated in FIG. 8. The
multiplexed signal is successively recorded on the recording medium
66 from a leading part of the multiplexed signal to a trailing part
of the multiplexed signal in a normal order. The leading part
corresponds to a leading one of the picture elements of the leading
picture or frame of the digital video signal while the trailing
part corresponds to a trailing one of the picture elements of the
trailing picture or frame of the digital video signal.
The decoding device 65 comprises a reproduction mode signal
generating circuit for generating a reproduction mode signal which
indicates a selected one of a normal reproduction and a reverse
reproduction in response to a request issued by an operator or
user. Responsive to the reproduction mode signal, an accessing
circuit 68 accesses the recording medium 66 so that the multiplexed
signal is read out of the recording medium 66 in the normal order
when the reproduction mode signal indicates the normal
reproduction. When the reproduction mode signal indicates the
reverse reproduction, the multiplexed signal is read out of the
recording medium 66 in a reverse order relative to the normal order
by the accessing circuit 68.
Responsive to the multiplexed signal, a demultiplexer 69
demultiplexes the multiplexed signal into the interframe predictive
error signal (namely, the first result of the basic predictive
coding) E, the intraframe coded signal (namely, the second result
of the intraframe coding) P, and the coding mode signal S. An
intraframe decoder 70 decodes the intraframe coded signal P into an
intraframe decoded signal P'.
Responsive to the reproduction mode signal, an alignment circuit 71
aligns each of the interframe predictive error signal E and the
coding mode signal S with the intraframe decoded signal P' only
when the reproduction mode signal indicates the reverse
reproduction. In this event, the alignment circuit 71 delays each
of the interframe predictive error signal E and the coding mode
signal S by a delay equal to a period of each picture or frame to
produce a delayed predictive error signal and a delayed mode
signal. When the reproduction mode signal indicates the reverse
reproduction, the alignment circuit 71 produces the intraframe
decoded signal P' as it is. When the reproduction mode signal
indicates the normal reproduction, the alignment circuit 71
produces each of the interframe predictive error signal E, the
coding mode signal S, and the intraframe decoded signal P' as it
is.
Responsive to the reproduction mode signal which indicates the
reverse reproduction, an inverter circuit 72 inverts the delayed
predictive error signal to produce an inverted predictive error
signal as an output signal thereof. When the reproduction mode
signal indicates the normal reproduction, the inverter circuit 72
produces, as the output signal thereof, the interframe predictivc
error signal E as it is. An adder 73 adds the output signal of the
inverter circuit 72 and a prediction signal 74 to produce an
interframe predictive decoded signal.
A selecting circuit 75 receives the coding mode signal S from the
alignment circuit 71 as a received mode signal when the decoding
device 65 carries out the normal reproduction. When the decoding
device 65 carries out the reverse reproduction, the selecting
circuit 75 receives the delayed mode signal from the alignment
circuit 71 as the received mode signal. When the received mode
signal indicates the intraframe coding, the selecting circuit 75
selects the intraframe decoded signal P' as a selected intraframe
decoded signal. When the received mode signal indicates the basic
interframe predictive coding, the selecting circuit 75 selects the
interframe predictive decoded signal as a selected interframe
predictive decoded signal. Thus, the selecting circuit 75 produces
the selected intraframe decoded signal and the selected interframe
predictive decoded signal collectively as a decoded video signal of
a digital form.
The decoded video signal is delivered to an external device for
reproduction of pictures. The decoded video signal is also
delivered to a delay circuit 76. The delay circuit 76 delays the
decoded video signal by a delay which is equal to a period of each
picture or frame. The delay circuit 76 thereby produces a delayed
video signal as the prediction signal 74.
The decoding device 65 carries out the normal reproduction of the
picture elements of the pictures of the digital video signal in
accordance with Formula (2) described above while the decoding
device 65 carries out the reverse reproduction of the pictures of
the digital video signal in accordance with Formula (3).
Referring to FIG. 14, a decoding device 65 is for decoding a
read-out signal read out of a recording medium 66 on which an
output signal (that is, the multiplexed signal) of the coding
device illustrated in FIG. 10 is successively recorded. The
decoding device 65 is similar to that illustrated in FIG. 13 except
for the following. The multiplexed signal further comprises the
motion vectors V. The demultiplexer 69 demultiplexes the
multiplexed signal into the interframe predictive error signal E,
the motion vector V, intraframe coded signal P, and the coding mode
signal S.
The alignment circuit 71 aligns only the interframe predictive
error signal E with the intraframe decoded signal P' only when the
reproduction mode signal indicates the reverse reproduction. In
this event, the alignment circuit 71 delays only the
motion-compensated interframe predictive error signal E by a delay
equal to a period of each picture or frame to produce a delayed
predictive error signal. The alignment circuit 71 produces the
motion vectors V as it stands regardless of the reproduction mode
signal.
A vector & mode processing circuit 77 receives the motion
vector V and the coding mode signal S. When the reproduction mode
signal indicates the reverse reproduction, the vector & mode
processing circuit 77 processes the motion vector V into a reverse
mode vector V' and further processes the coding mode signal S into
the reverse mode signal S" described above. The reverse mode vector
V' will later be described. When the reproduction mode signal
indicates the normal reproduction, the vector & mode processing
circuit 77 produces each of the motion vector V and the coding mode
signal S as it is. Either the reverse mode signal S" or the coding
mode signal S is delivered to the selecting circuit 75.
Responsive to the reproduction mode signal which indicates the
reverse reproduction, a gate 78 receives the reverse mode vector V'
to deliver the reverse mode vector V' to a variable delay circuit
79. When the reproduction mode signal indicates the normal
reproduction, the gate 78 inhibits delivering the motion vector V
to the variable delay circuit 79. The variable delay circuit 79
delays the inverted predictive error signal by a variable delay
which is varied in accordance with the movement represented by the
reverse mode vector V'. An output signal of the variable delay
circuit 79 is delivered to the adder 73. When the variable delay
circuit 79 receives no motion vector, the variable delay circuit 79
supplies the interframe predictive error signal E to the adder 73
as it is.
Another variable delay circuit 80 delays an output signal of the
delay circuit 76 by a variable delay which is varied in accordance
with the movement of the motion vector received from the vector and
mode processing circuit 77. The variable delay circuit 80 thereby
produces a delayed signal as the predictive signal 74.
The decoding device 65 carries out the normal reproduction of the
picture elements of the pictures of the digital video signal in
accordance with Formula (5) described above while the decoding
device 65 carries out the reverse reproduction of the pictures of
the digital video signal in accordance with Formula (6).
Turning to FIG. 15, a decoding device 65 is also for decoding a
read-out signal read out of a recording medium 66 on which an
output signal of the coding device illustrated in FIG. 10 is
successively recorded. The decoding device 65 is similar to that
illustrated in FIG. 14 except for the following
The variable delay circuit 79 is connected between the adder 73 and
the selecting circuit 75. The inverter circuit 72 is directly
connected to the adder 73. As a result, the interframe predictive
decoded signal is delayed by the variable delay circuit 79 by a
variable delay which is varied in accordance with the reverse mode
vector V'.
Another gate 81 is connected between the vector & mode
processing circuit 77 and the other variable delay circuit 80.
Responsive to the reproduction mode signal which indicates the
normal reproduction, the other gate 81 receives the motion vector V
to deliver the motion vector V to the variable delay circuit 80.
When the reproduction mode signal indicates the reverse
reproduction, the gate 80 inhibits delivering the reverse motion
vector V' to the variable delay circuit 80.
Turning to FIG. 16, the vector & mode processing circuit 77
comprises first and second multipliers 83 and 84. The first
multiplier 83 multiplies a horizontal component Vx by -1 to produce
a first multiplication result of multiplication. Likewise, the
second multiplier 84 multiplies a vertical component Vy by -1 to
produce a second multiplication result of multiplication. That is,
the first and the second multiplication results are identical with
first and second inverted components which are obtained by
inverting the horizontal and the vertical components Vx and Vy,
respectively.
It will be assumed that a picture element address corresponding to
a picture element location of the motion vector V is represented by
i, j. A first subtractor 85 subtracts the horizontal component Vx
of the motion vector V from a horizontal component j of the picture
element address to produce a first subtraction result a of the
subtraction. A second subtractor 86 subtracts the vertical
component Vy from a vertical component k of the picture element
address to produce a second subtraction result b of the
subtraction.
Supplied with a memory address which is indicated by the first and
the second subtraction results a and b, a memory 87 memorizes the
first and the second inverted components in the memory address.
Simultaneously, an input signal I is memorized in the memory 87 in
order to produce the reverse mode signal S". The input signal I
indicates the motion-compensated interframe predictive coding mode
and is of, for example, a logic "0" level.
When the coding mode signal S indicates the intraframe coding, the
first and the second inverted components and the input signal I
must not be memorized in the memory 87. For this purpose, the
coding mode signal S is supplied to an enable terminal of the
memory 87. As a result, the first and the second inverted
components and the input signal I are never memorized in the memory
87 when the coding mode signal S indicates the intraframe
coding.
After a lapse of a period of each frame or picture, the first and
the second inverted components and the input signal I are read out
of the memory 57 as the reverse mode vector V' (Vx, Vy) and the
reverse mode signal S" in response to a read-out address supplied
to the memory 87.
After the reverse mode signal S" is read out of the memory 87,
another input signal (not shown) representative of the intraframe
coding must be memorized in the memory 87 in order to produce a
following reverse mode signal S". The other input signal is, for
example, a logic "1" level to represent the intraframe coding. For
this purpose, a content of the memory 57 is erased when the memory
57 receives a frame pulse which is generated in synchronism with a
leading part of each frame.
The reverse mode vector V' (Vx, Vy) and the reverse mode signal S"
are delivered to a selector 88. When the selector 88 receives from
the reproduction mode generating circuit 67 the reproduction mode
signal which indicates the normal reproduction, the selector 88
selects the coding mode signal S and the motion vector V to deliver
the coding mode signal S and the motion vector V to external
circuits. When the reproduction mode signal indicates the reverse
reproduction, the selector 88 selects the reverse mode vector V'
(Vx', Vy') and the reverse mode signal S" to deliver the reverse
mode vector V' (Vx', Vy') and the reverse mode signal S" to the
external circuits.
Turning to FIG. 17, the vector & mode processing circuit 77 is
similar t that illustrated in FIG. 16 except that a multiplexer 89
is connected between the memory 87 and a pair of multipliers 83 and
84 and a demultiplexer 90 is connected between the memory 87 and
the selector 88.
Responsive to the motion vector V (Vx, Vy), a pair of the
multipliers 83 and 84 produces an inverted motion vector. The
multiplexer 89 multiplexes the inverted motion vector and the
coding mode signal S into a multiplexed signal. The multiplexed
signal is memorized in the memory 87.
The multiplexed signal is read out of the memory 87 as a read-out
signal. The demultiplexer 90 demultiplexes the read-out signal into
the motion vector V (Vx, Vy) and the coding mode signal S. The
motion vector V (Vx, Vy) and the coding mode signal S is delivered
to the selector 90.
On multiplexing the inverted motion vector and the coding mode
signal S, use is made of the fact that no motion vector is present
or produced for an intraframe mode. A motion vector which is not
existent in fact is used as the coding mode signal which indicates
the intraframe mode. Supposing that the motion vectors are
restricted to a predetermined area of (+15, +15), an exceptional
motion vector of (-16, -16) is used as the coding mode signal which
indicates the intraframe mode. The exceptional motion vector is
treated as a specific example of the motion vectors. After the
signals are read out of the memory 87, it is necessary to update
the memory 87 so as to have the exceptional motion vector of (-16,
-16) whenever the memory 87 is supplied with the frame pulse.
* * * * *